Carbon footprint (CF) has become a crucial piece to develop strategies to tackle the climate change issue. Its implementation makes it possible establishing a path towards decarbonisation with the aim to comply with European and global greenhouse gases (GHG) emissions guidelines and commitments. Currently, several tools for calculating the CF are available. However, the differences in the calculation methodology and data collection prevent comparative studies based on the results obtained to be made. For this reason, CEDEX (Centro de Estudios y Experimentación de Obras Públicas), commissioned by Puertos del Estado, prepared a good practice guide with a common methodology for calculating the CF of Spanish Ports. In this study, we tested this standardized methodology for the first time in the Port of Vigo (NW Spain) during a four-year period (2017–2020), developing a web tool to facilitate its application, with the ultimate aim to extend its implementation nationwide. This work demonstrates the suitability of the CEDEX methodology to quantify the CF in harbours, and to assess the interannual evolution of the emissions, thus facilitating the assessment of the different environmental strategies implemented in the port to achieve the emissions reduction targets. The main CF loads are derived from the loading/unloading operations, due to the consumption of fuel, accounting to a value of 14,161 kg CO2 eq per TEU (twenty-foot equivalent unit). With the implementation of the methodology developed in this study, a reduction of 55 % of GHG emissions could be achieved in all port activities, thus complying with the objectives of the European Green Deal for 2030.